Resin-impregnated woven textile fabric and method of producing the same



`Maly 14, 1946. R. c; WHITMAN 2,400,379

RESIN-IMPREGNATED WOVEN TEXTILE FABRIC AND METHOD OF' PRODUCING THE SAMEFiled Sept. l5, 1944 Fig. 2.

i@ WM@ IN V EN TOR.

i Patented May 14, 1946 RESIN-IMPREGNATED FABRIC AND METHOD F PRODUCINGTHESAME WOVEN TEXTILE Ross C. Whitman, Walpole, Mass., assigner to TheKendall Company, Boston,

Mass., a corporation of Massachusetts Application September 15, 1944,Serial No. 554.279

12 Claims.

This invention relates to resin-impregnated woven textile fabrics andmethods of making the same, and the object of the invention is toprovide improved fabrics of this type having moisture-resistantstiffness and which have substantially no tendency to curl. Theprincipal commercial applications of the invention are found in thefield of mechanical or industrial fabrics, particularly fabrics whichmay be subject to conditions of high humidity and temperature, forexample, radio spiders. The fabrics hereof are also useful for condenserand insulating cloths, interlinings, hat materials, shoe linings, andlaminated fabrics commonly made from muslins, drills, twills, andsheeting materials.. Resin-impregnated fabrics as heretofore known andused in the art have curled to a substantial extent and the presentinvention provides a satisfactory and certain basis for substantiallyeliminating such objectionable 'curling during not only cutting andfabrication into various articles of manufacture (which is sudicient formany purposes) but also during the utilization thereof, for example,fabrics which must retain a certain stiffness even where subject tosevere atmospheric conditions of heat and moisture.

The present invention provides novel resinimpregnated fabrics in whichundesirable curl is overcome and this latter condition is maintaineddespite atmospheric changes and provides a ready method of producingsuch fabrics without lthe use of special equipment and without`substantial increase in manufacturing cost. In accordance with myinventions as more fully described in my co-pendlng applications. SerialNumbers 512,211 and 525,719, filed November 11, 1943, and March 9, 1944,respectively, the factors which inuence fabric curl in stiifened fabricsare yarn size of component yarns as the maior factor and, as otherfactors, direction and degree of yarn twist, and the number of yarn endsper inch of fabric in the warp and filling directions. Also, as setforth in said applications, the sets of warp and filling yarns have aprofound relationship and effect inter se and the fabric curling ortorque effect exerted by a given warp yarn can be and is neutralized oroffset by the curling effect of a lling yam of the same size and thesame twist (same number of turns per inch and same direction of twist),and, further, the curling effect of one set of yarns (warp or filling)can be neutralized by the other set of yarns whether of unidirectionaltwist or whether including yarns of both directions of twist, and

though said other set also differs from the first set in yarn size, intwist multiple, and in number of yarns per inch of fabric, thedid'erence occurring in two or more of the factors. The method ofpracticing the present invention by incorporating my said discoveries inthe manufacture of resin-impregnated moisture-resistant fabrics havingsubstantially no tendency to curl is fully set forth hereinafter.

Study of certain stlifened fabrics. including the resin-impregnatedceilulosif: fabrics of this invention, resulted in the paradoxicaldiscovery that in such fabrics the curl is caused by an increase in thetwist (i. e.. a twisting tighter) of the dominant component yarns. theseyarns imparting a. net curling effect even though the same set of yarnsinclude stldened yarns of opposite twist. For example. when a footSquare Jpiece of a certain commercial resin-impregnated fabric was laidupon a flat surface, it was observed to curl in that two of the diagonalcorners lifted up somewhat from the nat surface and the other twodiagonal corners attempted to curl downwardly. IIhe curi here was causedby a twisting tighter of certain component yarns.

By properly applying these discoveries in yarn manufacture andselection. in weave layout and weaving of textile fabrics for resinimpregnation, one canproduce a wide range of novel reninimpregnatedstiffened moisture-resistant fabrics (with warp and iilllng of the sameor opposite directions of twist) which are characterised by asubstantial absence of curl even though resinimpregnated and by amoisture resistance such that the fabric retains a high stiffness evenwhen thoroughly wetted.

In the drawing, showing preferred types of fabrics of this invention,

Fig. 1 is an enlarged diagrammatic view illustrating a resin-impregnatedsquare weave fabric of unidirectional twist; and

Fig. 2 is a diagrammatic view illustrating a resin-impregnated fabricwherein one not of yarns is unidirectional and the other set includesyarns of opposite direction of twist.

Referring to the drawing in which like numerals represent like parts,Fig. 1 illustrates a noncurling resin-impregnated fabric of thisinvention with cellulosic Z-twist warp yarns t of smaller size than thecellulosic filling yarns' I with the latter equal in number of ends but0f lower degrec (not shown) of unidirectional Z-twist, in which bothsets of yarns tend to twist tighter because of their resin-impregnation,the tendency of the warp yarns I to lift the diagonal opposite lower andupper corners of the fabric, as oriented in the drawing, beingneutralized by the filling yarns 3 so that the corners all lie fiat andthe fabric does not curl.

Fig. 2 shows another example of resin-impregnated non-curling fabric ofthis invention with cellulosic warp yarns l-Z and I-S of opposingtwists, there being nve yarns l-Z for each yarn t-S as shown. These warpyarns are of larger size than the unidirectional Z-twist cellulosicfilling yarns 5, with the latter equal in number of ends with therequired degree of twist (not shown) in which both sets of yarns tend totwist tighter because of the resin-impregnation, the net tendency of thewarp yarns to lift the lower and upper corners being neutralized by theset of fllling yarns so that the corners of the fabric all lie fiat andthe fabric does not curl despite the resin-impregnation.

Nearly all woven textile fabrics have as many or more warp yarns thanlling yarns so that, from the standpoint of end count, most V(but notall) typical applications of the invention fall in between a squareweave fabric. with its equal number of ends per inch of warp and fillingyarns, and a fabric with a two-to-one or higher ratio of warp to fillingends per inch, though the invention is also applicable to fabricswherein the number of lling ends per inch exceeds that of the warp.Also, for similar reasons of economical and practical manufacture onmodern spinning and weaving equipment, nearly all fabrics heretofore.particularly industrial fabrics, have larger warp yarns than nllingyarns. For the same reasons, warp twist has been almost invariablyhigher than filling twist. in the trade, "warp twist is synonymous withhigh twist, and filling twist is synonymous with low twist.

Ihe foregoing principles of the invention afforded a basis for myderivation of a mathemati cal equation which, as a practical matter,gives a general guide for successful application and -use of theinvention in the actual manufacture of the resin-impregnated non-curlingfabrics of this invention. The basic equation is as follows:

Ell=

where M is twist multiple, N is yarns number (size), E is end count, andw and l refer to warp and filling, respectively.

In the use of the equation for fabric design and manufacture after thegeneral construction as to end count and yarn size has been determined.the equation is applied first only to warp and filling yarns ofunidirectional twist whether the fabric be simply unidirectional orwhether it have unidirectional yarns in but one of the two sets ofyarns. Ii' the latter type. the equation is applied first to theunidirectional set of yarns (whether such set he filling, as usuallypreferred. or warp) and to the yarns of the same direction of twist inthe other or second set and to solve the equation so as to determine thenumber of such latter yarns necessary to neutralize the fabric curlingtendency of the first set. The remaining yarns of said second set arethen divided equally into yarns of each direction of twist (it beingassumed that all the yarns of said second set are of the same size andtwist multiple). Referring to the fabric of Fig. 2. for example. theequation is rst applied to filling yarns of unidirectional Z-twist andthe required number of warp yarns of the desired size of the samedirection of twist necessary to neutralize the fabric Vcurling tendencyof said filling yarns is determined, here four warps per six fillings.This leaves two warp yarns for each basic unit of this fabricconstruction, which two warp yarns are then divided into i-S and IZ, allof the warp yarns in this example being of the same size and twistmultiple. This gives the square weave fabric as shown in Fig. 2 in whichthere are six Z-twist filling yarns for six warp yarns made up of veZ-twist yarns and one S-twist yarn.

Normally, as inthe preferred fabrics of this invention. at least one setof yarns is of unidirecnecessary, and, similarly, important advantagesare lost in so doing.

Where each set includes yarns of opposing twist (as well as where butone set does). the basic equation may be applied to give the net fabriccurling effect of each set as follows:

[rzvy-lliffiilf where M equals twist multiple, N equals yarns number, Eequals end count. w and f refer to warp and nlling respectively. and Zand B refer to the respective directions of twist.

If either set of yarns includes yarns differing from each other in sizeor twist multiple. it will be necessary to consider each group ofsimilar yarns separately and add together the results thereof to obtainthe total net factor for each set. The twist multiple employed in thisequation is the same as that employed in the textile art and equalstwist turns Der inch of yarn divided by the square root of the yarnnumber` (cotton system), and for the purpose of the equation, and in thespecification and claims, the size of all yarns is expressed on thecotton system. for example, 350 denier rayon yarns are classifiedapproximately as number 15.2; and the expression end count" is to betaken as meaning the number of yarns per inch of fabric in thedesignated direction. In the application and use of the invention. itisnot necessary strictly to adhere to absolute equality as variations fromthe equality represented by the equation are necessarily encountered inpractice, the ultimate test being whether any given fabric embodies theprinciples and features of the invention as herein described and`claimed.

1n accordance with this invention, there is applied to the originalfabric water or solventcarried potentially water-insoluble resin orresinforming materials. Various resins such as phenol formaldehyde, ureaformaldehyde, melamine formaldehyde, protein (e. g. casein) formaldeplethat the value of filling when measured at 70 to retain y57% of theseresin `materials are water-insoluble when applied, or are renderedwater-insoluble after application (by usually) the stiffness obtained isnot immediately or readily removed when the fabric is washed. Thedetermining factor in the choice of the resin and its method ofapplication is that water must baking 'the impregnated fabric,

be present during the polymerization of the resin and the consequentstiifening of the fabric. This water may be formed as a product of thecondensation of the resin or may be present in the liquid impregnatingmixture as a solvent or a carrier.

The impregnatlng materials should be applied in sufficient quantity andconcentration so that the resultant end product includes 20 to 150% byweight of resin (based on the weight of the fabric) in order to providethe desired moisture-resistant properties. In the preferred practice ofthis invention, when thoroughly wetted. for example, for l minutes inwater at 70 F., the fabric possesses a stiffness of more than 50% of itsstiffness at 32% relative humidity at the same temperature. Thiscorresponds with e, piece of fabric 4at van ordinary outdoortemperature, being very dry, as compared with being subject to extremesof humidity or moisture. This is a typical condition encountered vinradio loud speakers, e. g.. at sea or under tropical conditions underwhich the resin-impregnated fabric membrane :mustV maintainsubstantially its original degree of stiff- 'ness measured immediatelyafter theresin has been cured or poiymerized. Such stiffness may beconveniently expressed in units of mean exural rigidity (milligramcentimeters) as incident to a standard Pierce Plexometer, and thesainetypical fabrics with their weights andstiness are as follows:

example 1 A heavy stii'i'ened fabric used for stamping out the crown andbrimof men's summer hats was found to have objectionable curlingcharacter-v istics, which not only made the cutting operation dimcult,but also gave the brim an uneven roll. This base fabric had an actualend count of 20.1 x 17.9 with 3%s yarns in the warp and 4's in thefilling, the corresponding twist multiples being 4.25 and 3.27. Byaltering the specications so that the yarn weights were 3.93 in the warpand 3.19 in the filling, and keeping the same end count and fillingtwist multiple, it was found by solving the equation for the warp twistmulti- 4.07 would give a fabric with a warp preponderance of only .003.This fabric when resin-impregnated according to the teaching of curl,and ture.` The average showed exceptional resistance to moisiiexuralrigidity of warp and F. and 32% relative humidity was 45,000, when theresin content based on the weight of the fabric was 35%. After soakingthe sample in water at the same temperature for iifteen minutes. therewas no apparent loss in stiffness.

` Example 2 A. non-curling resin impregnated batiste with an end countof approximately the stillness measured at 70 F. and 32% relativehumidity after it hadV been soaked for fifteen minutes in water at 70 F.This fabric had a resincontent of 98% based on the weight of theuntreated fabric and the flexural rigidity measured under the initiallystated ecn- 88 x 00 was found this application exhibited no tendency t0ing employed dition was 2300. In setting up the specifications for thisfabric so that a non-curling cloth would result, it was found that themethod of balancin the previous example could not be used here. The yarnweights in this fabric lare 69.9ls in the warpand 95.32s in the ailing.Substituting these along with the actual end count of 67.6 x 79.3 andthe twist multiples of 5.56 in the warp and 5.12 inthe nlling in theformula gives a. filling value of .3136, compared with a warp value of.7298. In order to bring these values close enough to produce anon-curling fabric.the yarn numbers and other values would have to bevery considerably changed. Rather than do this, the fabric may yarns inthe warp and only Z yarns in the filling. The ratio of B and l yarns inthe warp may be found in the following way, the number oi ends per inchof Z twist yarn required in the warp to exactly balance the filling willbe found by setting the warp side of the equation equal to the fillingvalueY which has already been found and solving for E. This is found inthis case to be 40.7 ends per inch. subtracting 40.7 from 87.6, thetotal lwarp count gives 46.9 ends per inch which must .be balanced andtherefore equally divided between Example 3 A radio spider which liesfiat may be stamped from a resin impregnated non-curling 64 x 60 fabric.This fabric which has an actual end count of 63.0 x 59.0 with 29.81'syarns in the warp and 29.925 yarns in the filling may be balanced byproperly adjusting the twist multiples. If the warp twist multiple istaken as 4.10, the warp value calculates to be 1.431. If the nlling isthen given a twist multiple of 4.31. the filling formula value is 1.392and the warp preponderance is only .039 which is low enough to give abalanced noncurling fabric. A'Ihe flexural rigidity of this fabric whenimpregnated with a phenol formaldehyde solution so that the resincontent based on the weight of the base fabric is is 7.500 measured atF. and 32% relative humidity. After soaking in water in the same testapplied in the previous examples, 60% of the stiffness is retained.

- 'Example 4 A 70 x 40 drill suitable for use as a shoe lining may betreated with a resin so that the resin content of the fabric will be 29%based on the weight of the untreated fabric, and the flexural rigiditymeasured under the usual conditions,

' that is, '10 F. and 32% relative humidity, will be 400. Virtually allof this sti'ness is retained even after the usual soaking treatment.Freedom of this fabric from curl may be assured by setting be balancedby using both S and Z filling value, calculated from the fillingspecification of 38.9 ends per inch with 15.95s yarns with a twistmultiple of 3.59. we find that 23.3 ends of 13.48.*s warp yarns with atwist multiple of 4.55 are needed to balance the filling. Since thedesired number of ends per inch in the warp is actually 69.3. thedifference must be equally divided between S and Z yarns. A tie-in ofone S yarn to two Z yarns in the warp will approximately accomplishthis, giving a fabric which has a filling preponderance of .016 andwhich is therefore essentially non-curling.

Example 5 A heavy 52 x 36 duck, resin-treated to give it amoisture-resistant stiff finish. may be made to lie flat by making itaccording to the following specifications. The original fabric had anactual end count of 51.6 x 35.8 and calls for the use in the warp of9.03s yarns with a twist multiple oi 4.01 and in the filling of 11.52syarns with a twist multiple of 3.46. These values will give a warpfigure of 7.359 and a filling value of 3.012 which indicates that thefabric is way out of balance and that the more satisfactory way ofmaking it non-curling requires the use of oppositely twisted yarns inthe warp. Using the given filling value and the yarn number and twistmultiple of the warp yarns. it is found that 21.1 ends per inch arerequired to balance the filling. If the rest of the yarns are equallydivided between S and Z twist, there will be 36.35 ends per inch of Ztwist yarn and 15.25 ends per inch of 8 twist yarn, which is found tocorrespond quite closely to a ratio of two S twist yarns to ve Z twistyarns. With this warp tie-in. the fabric is found to have a warppreponderance of .142 which is sufficiently small to give a non-curlingfabric. The resin treatment accorded this fabric which consisted of theapplication of enough resin solution so that the resin content of thefinished fabric was 60% based on the weight of the untreated cloth,resulted in the fabric exhibiting a flexural rigidity of 365.000 at 70F. and 32% relative humidity. After soaking in water at 70 F'. forfifteen minutes. this resin-impregnated duck retained 62% of itsoriginal stiffness.

Example 6 A non-curling viscose cotton blend (60% viscose and 40%cotton) may be given a moisture; resistant stiff finish by treating itwith a melamine formaldehyde resin so that the resin content of thestiffened fabric is 53% based on the weight of the untreated cloth. Thisfabric has a flexural rigidity of 34,000 when measured at 32% relativehumidity and 70 F. and 70% of this stiffness is retained after thefabric has undergone the soaking treatment described in the previousexamples. This fabric has an actual end count of 43.9 by 41.5 and has14.87s yarns in the warp and 12.11's yarns in the filling. It was foundthat the fabric could be balanced without resorting to the use ofoppositely twisted yarns in the warp by suitably adjusting the twistmultiples. A twist multiple of 4.47 in the warp and of 3.40 in thefilling will give warp and filling values such that the werppreponderance will be .076. Because of this low value, the fabricembodying these specifications will lie fiat.

Example 7 A stliened condenser fabric which is resistant to moisture andwhich will not curl under any condition may be made by treating a 76 x72 lawn with a melamine formaldehyde resin so that the resin content isbased on the weight of the untreated fabric. The flexural rigidity ofthis fabric, the specifications for which are given below. is 1,300 whenmeasured under the usual conditions, and only 20% less when measuredafter the fabric has been soaked in water for fteen minutes at 70 F. Inorder that the fabric be non-curling. the specifications are set up inaccordance with the equation for balanced fabrics. When the end count,yarn numbers, and twist multiples, 75.8 x 71.3; 59.52s, 85.41'5; 4.45,3.39, respectively, for a standard fabric of this type are substitutedin the equation, it is seen the warp value is .5860 and the fillingvalue .1897. This is, of course, far from a non-curling fabric. Becauseit is desirable to keep essentially the appearance and characteristicsof this fabric, however, it seemed advisable to balance this fabric byusing alternate S and Z yarns in the warp. By carrying out similarcalculations to those used in Example 2, it was discovered that a warptie-in of one S yarn to every two Z yarns would give a fabric with awarp preponderance of only .005, and consequently a non-curling fabric.

The resins may .be applied to fabrics made of any type of cellulosic orpredominantly cellulosic textile fabrics plain or mixed or to plain ormixed yarns including staple or cut staple natural or syntheticcellulosic fibers. or continuous cellulosic filaments (later referredto). Though non-cellulosic synthetic or natural libres or filaments maybe included in minor proportions, it must be borne in mind that in noneof these non-celluloslc fibres does a water-swell ing and stifl'eningwith resultant reversal of curl occur, as in the predominant cellulosicfibres.

The preferred impregnated fabrics of this invention are made fromfabrics woven from or including yarns made up of, or which includepredominantly cotton or other natural cellulosic fibres such as sisal.rai'nie, hemp or jute, or synthetic celiulosic fibres such as viscose,cuprammonium and other regenerated cellulosic fibres (either cut stapleor continuous filament).

Various impregnated fabrics may be made which include a. substantialproportion of yarns in the warp, filling. or both, which are not swollenand stiiiened so as to produce a reverse curl (yarns twisting tighter),in such fabrics the warp and filling each including swollen andstiifened yarns with their reverse fabric curling tendencies offset ingeneral accordance with the foregoing disclosure. In such cases thecurling effect of the proportion of yarns not producing` reverse curlmay be safely disregarded as not significant in view of their relativelynegligible effect upon curling as compared with that of the pronouncedand very much greater curling effect of the swollen and stiifened warpand filling yarns producing reverse curl.

In the practice of this invention, it is important to provide warp yarnsand filling yarns that are spun with precision from uniform card sliverto definite sizes and twist multiples, and so woven that all areas ofthe body of the fabric are strictly uniform in construction since it isthese factors, and their relation to each other, that are depended uponin arriving at the desired result. Even with the most modern equipment.and with carefully controlled spinningroom humidity. it is well knownthat considerable variation in the yarn size occurs as spinningproceeds. A spinning machine balanced and adiusted to produce 30s yarnsmay, after a week or ten days operation, be found to be delivering asfine as 35s or 36s, or as heavy as 27's or 26s, the shift toward lighteryarns usually proceeding faster and further than the shift towardsheavier yarns. These variations are usually explained as resulting fromhumidity changes, temperature changes, stock changes, and machine wear,producing maladjustments.

Standard practice in modern textile mills calls for the analysis ofyarns approximately every two weeks, and the readiustment f yarns sizeprescribed is made usually on the first roving frame. usually called theslubber," or the second roving frame, known as the first intermediate."This measure of control is satisfactory for ordinary fabric manufacture,but since it would permit drifting of yarn size to the extent mentionedabove, it is obvious from the equation underlying this invention that itis entirely inadequate for the practice of the invention. Also, anychange in yarn size produces a significant change in twist multiplesince the spinning-frame delivers a fixed number of turns pr inch to theyarn, rather than a xed twist multiple. In the manufacture of fabrics ofthis invention, it is recommended that yarn analyses and equipmentadjustment as needed be made daily, usually at the second drawing framerather than on any of the succeeding roving frames. In addition, specialcare should be taken in the control of spinning-room humidities. etc.

In making use of the equation, actual yarn sizes, as determined byanalyses in the spinning-room, and actual twist multiples, as determinedby well known formulas involving spinning-frame gears, should be usedrather than the "theoretical or "standar-d values. Similarly, actual endcounts as reported by the weave room should be used. It is found thatusually the slight changes in the end counts occasioned by variations intension on the loom are not troublesome providing the cloth tension ischecked and adjusted daily in the usual way. For fabrics where asubstantially complete absence of curl is the requirement, as in radiospiders, it is found that the old style friction let-od on the loom isto be preferred to automatic positive let-of! mechanism, such as theRoper-Diaper" or Bartlett," which permit greater variations in endcounts since they control tension with less precision, generally. Also,reasonable care should be taken to avoid any considerable distortion ofthe woven "neutralizew fabric in subsequent finishing processes. Withfairly equal tensions therein so that the end count in the finishedfabric is roughly equally higher or equally lower in both the warp andthe nlling, however, no trouble need be anticipated on this portingsurface, not to exceed 1% inches. The

preferred and most searching test for base ce1- lulosic fabrics ofcotton and/or viscose rayon is by first impregnating the fabric in asolution made up ls follows:

Bakelite, 60% methyl alcohol); 4 Methyl alcohol 1 Water a- 5 The pick-upof the solution by the base fabric may, for example, be from to 150% byweight (on the weight of base fabric). The sample is then pressedbetween two heated metallic surfaces (net total pressure 10 lbs.) at atemperature of approximately C., for sixty seconds, in order tocompletely polymerize and set the resin, thus forming a product of thisinvention. The sample is then at once removed and placed withoutrestraint on a horizontal surface, such as a table, and promptlyobserved. Since this test is so searching, as a practical matter, thefabrics of this invention so made may be regarded as havingsubstantially no tendency to curl if the sample remains substantiallyextended and no corner thereof rises more than 1 to 1% inches above thesupporting horizontal surface upon which it was placed. Fabrics made inaccordance with the preferred practice of this invention incorporatingtherein any of the resins mentioned above are well within the amountmentioned. The impregnating materials hereinbefore referred to asemployed in ordinary commercial use will not cause the rise of a cornerof a five inch test square more than V2 to 1 inch above the supportinghorizontal surface.

Having thus described my invention, what I desire to claim as new is:

l. A textile material adapted for industrial use comprising aresin-impregnated stiffened woven fabric having substantially notendency to curl, composed essentially of sets of twisted cellulosicyarns and a resinous impregnation to at least 20% of the original basefabric weight, including aset of warp yarns and a set of filling yarns.with the yarns of both of said sets uniformly dispersed and arrangedthroughout the body of the fabric, said sets and yarns thereof being sorelated with respect to twist direction, twist multiple, yarns numberand count as to produce substantially the equality represented by theequation ci El ,ci El i/T s Nr z ,f 20% of the original base fabricweight, including a set of Warp yarns and a set of filling yarns, withthe yarns of both of said sets uniformly dispersed and arrangedthroughout the body of the fabric, at least one of said sets including asubstantial number of yarns or each direction of twist, said sets andyarns thereof being so related with respect to twist direction, twistmultiple, yarns number and count as to produce substantially theequality represented by the equation itrile-fifi= where M equals twistmultiple, N equals yarns number, E equals end count, w and f refer towarp and nlling, respectively, and Z and S refer to right and left-handtwist, respectively, thereby providing an impregnated fabric having aneutralized curling tendency and moisture-resistant stiffnesscharacteristics,

3. A textile material adapted for industrial use comprising aresin-impregnated stiifened woven fabric having substantially notendency to curl, composed essentially of sets of twisted cellulosicyarns and a resinous impregnation to at least 20% of the original basefabric weight, including a set of warp yarns and a set of filling yarns,with the yarns of both of said sets uniformly dispersed and arrangedthroughout the body of the fabric, both of said sets including asubstantial number of yarns of each direction of twist, said sets andyarns thereof being so related with respect to twist direction, twistmultiple, yarns number and count as to produce substantially theequality represented by the equation where M equals twist multiple, Nequals yarns number, E equals end count, w and f refer to warp andfilling, respectively, and Z and S refer to right and left-hand twist,respectively, thereby providing an impregnated fabric having aneutralized curling tendency and moisture-resistant stiffnesscharacteristics.

4. A textile material adapted for industrial use comprising aresin-impregnated stiifened woven fabric having substantially notendency to curl, composed essentially of sets of twisted cellulosicyarns and a resinous impregnation to at least 20% of the original basefabric weight, including a set of warp yarns and a set of filling yarns,with the yarns of both of said sets uniformly dispersed and arrangedthroughout the body of the fabric, both of said sets having yarns ofunidirectional twist. said sets and yarns thereof being so related withrespect to twist direction, twist multiple, yarns number and count as toproduce substantially the equality represented by the equation where Mequals twist multiple, N equals yarns number, E equals end count, w andJ* refer to warp and filling, respectively, and Z and S refer to rightand left-hand twist, respectively, thereby providing an impregnatedfabric having a neutralized curling tendency and moisture-resistantstiffness characteristics.

5. A textile material adapted for industrial use comprising aresin-impregnated stifiened woven fabric having substantially notendency to curl, composed essentially of sets of twisted cellulosicyarns and a resinous impregnation to at least 20% of the original basefabric weight, including a set of warp yarns and a. set of fillingyarns, with the yarns of both of said sets uniformly dispersed andarranged throughout the body of the fabric, said set and yarns thereofbeing so related with respect to twist direction, twist multiple, yarnsnumber and count as to produce substantially the equality represented bythe equationY [cree] ,[d

nu s W71 where M equals twist multiple, N equals yarns number, E equalsend count, w Aand f refer to warp and filling, respectively, and Z and Srefer to right and left-hand twist, respectively, thereby providing animpregnated fabric having a neutralized curling tendency andmoistureresistant stiiiness characteristics, said fabric after wettingfor l5 minutes in water at 70 F. exhibiting at least two-thirds of itsstiness in an atmosphere of 30% relative humidity at 70 F.

6. A textile material adapted for industrial use comprising aresin-impregnated stiifened woven fabric having substantially notendency to curl, composed essentially of sets of twisted cellulosicyarns and a resinous impregnation to at least 20% of the original basefabric weight. including a set of warp yarns and a set of filling yarns,with the yarns of both of said sets uniformly dispersed and arrangedthroughout the body of the fabric, at least one of said sets including ay substantial number of yarns of each direction M-erlycfsrf] v Nw Nrwhere M equals twist multiple, N equals yarns number, E equals endcount, w and f refer to warp and filling, respectively, and Z and Srefer to right and left-hand twist, respectively, thereby providing animpregnated fabric having a' neutralized curling tendency andmoistureresistant stiffness characteristics, said fabric after wettingfor l5 minutes in water at 70 F. exhibiting at least two-thirds of itsstiffness in an atmosphere of 30% relative humidity at 70 F. 7. Atextile material adapted for industrial use comprising aresin-impregnated stiffened woven fabric having substantially notendency to curl, composed essentially of sets of twisted cellulosicyarns and a resinous impregnation to at least 20% of the original basefabric weight, including a set of warp yarns and a set of filling yarns,

andere with the yarns of both of said sets uniformly dispersed andarranged throughout the body of the fabric. both of said .sets includinga substantial number of yarns of each direction of twist, said sets andyarns thereof being so related with respect to twist direction, numberand count as to produce substantially the equality represented by theequation i where M equals twist multiple, N equals yarns number, Eequals end count, w and f refer to warp and filling, respectively, and Zand S refer to right and left-hand twist, respectively, therebyproviding an impregnated fabric having a neutralized curling tendencyand moisture-retwist multiple, yarns sistant stiffness characteristics,said fabric afterv Y' wetting for l5 minutes in water at 70 F.exhibiting at least two-thirds of its stiffness in an atmosphere of 30%relative humidity at 70 F.

8. A textile material adapted for industrial use comprising aresin-impregnated stiffened woven fabric having substantially notendency to curl, composed essentially of sets of twisted cellulosicyarns and a resinous impregnation to at least 20% of the original basefabric weight, including a set A`of warp yarns and a set of fillingyarns, with the yarns of both of said sets uniformly dispersed andarranged throughout the body ofthe fabric, both of said sets havingyarns of unidirectional twist, said sets and yarns thereof being sorelated with respect to twist direction, twist multiple, yarns numberand count as to produce substantially the quantity represented by theequation where M equals twist multiple, N equals yarns number, E equalsend count, 1v and f refer to Warp and filling, respectively, and Z and Srefer to right and left-hand twist, respectively, thereby providing animpregnated fabric having a neutralized curling tendency andmoistureresistant stiffness characteristics, said fabric after wettingfor l5 minutes in water at 70 F. exhibiting at least two-thirds of itsstiffness in an atmosphere of 30% relative humidity at 70 F.

9, The method of producing a woven fabric for industrial uses havingmoisture-resistant stiffness characteristics and substantially notendency to curl which consists in spinning, selecting, and weaving aset of uniform warp yarns and a set of uniform filling yarns, the warpyarns being so related to the filling yarns with respect to twistdirection and multiple, yarn number and count as to producesubstantially the equality represented by the equation where M equalstwist multiple. N equals yarns number, E equals warp and fillingrespectively, and Z and S refer to the respective directions of twist,and then impregnating said fabric with a resinous medium amounting to 20to 150% fabric weight, thereby providing an impregnated fabric havingsaid neutralized curling tendency and moisture-resistant stiffnesscharacteristics.

10. The method of producing a woven fabric for industrial uses havingmoisture-resistant stiffness characteristics and substantially notendency to curl, which consists in spinning, selecting, and Weaving aset of uniform warp yarns and a set of uniform filling yarns, at leastone of said sets being of unidirectional twist, the warp yarns being sorelated to the filing yarns with respect to twist direction andmultiple, yarn number and count as to produce substantially the equalityreprerrr-yur N N/Nw s VNfa z where M equals twist multiple, N equalsyarns number, E equals end count, w and f refer warp and fillingrespectively, and Z and S refer to the respective directions of twist,and then lmpregnating said fabric with a resinous medium amounting to 20to 150% of the original base fabric weight, thereby providing animpregnated fabric having said neutralized curling tendency andmoisture-resistant stiffness characteristics. l1. The method ofproducing a woven fabric for industrial uses having moisture-resistantstiffness characteristics and substantially no tendency to curl, whichconsists in spinning, selecting, and weaving a set of uniform Warp yarnsand a set of uniform filling yarns, at least one of said sets includinga substantial number of yarns of each direction of twist, the warp yarnsbeing so related to the filling yarns with respect to twist directionand multiple, yarn number and count as to produce substantially theequality represented by the equation:

where M equals twist multiple, N equals yarns number, E equals endcount, w and f refer to warp and filling respectively, and Z and S referto the respective directions of twist. and then impregnating said fabricwith a. resinous medium amounting to 20 to 150% of the original basefabric weight` thereby providing an impregnated fabric having saidneutralized curling tendency and moisture-resistant stiffnesscharacteristics.

l2. The method of producing a woven fabric for industrial uses havingmoisture-resistant stiffness characteristics and substantially notendency to curl which consists in spinning, selecting, and weaving aset of uniform warp yarns and a set of uniform filling yarns, both ofsaid sets including a substantial number of yarns of each direction oftwist, the warp yarns being so related to the filling yarns with respectto twist direction end count. w and f refer to` of the original base andmultiple. yam number and count as to produce substantially the equalityrepresented by the equation:

:lil on N., N (ih-nal@ (Mf-s E' lo Certicate of Correction Patent No.2,400,379. May 14, 1946.

ROSS C. WHITMAN y certified that errors appear in the printedspecification of the above patent requiring correction as follows: Page6, second column, line 12, claim set read sets; pa e 7, first column,line 39, claim 8, for` quantity read equality;

age 7, second column, lzine 17, claim 10, for filing read filling; page8, first column, oe 11, claim 12, for that portion of the formulareading :H: read :1s-+I: and that the said Letters Patent should be readwith th e same may conform to the record of the case in the Pa Signedand sealed this 10th day It is hereb numbered 5, for

ese corrections therein that tent OHce.

of September, A. D. 1946.

LESLIE FRAZER,

First Assistant Commissioner of Patents.

and multiple. yam number and count as to produce substantially theequality represented by the equation:

:lil on N., N (ih-nal@ (Mf-s E' lo Certicate of Correction Patent No.2,400,379. May 14, 1946.

ROSS C. WHITMAN y certified that errors appear in the printedspecification of the above patent requiring correction as follows: Page6, second column, line 12, claim set read sets; pa e 7, first column,line 39, claim 8, for` quantity read equality;

age 7, second column, lzine 17, claim 10, for filing read filling; page8, first column, oe 11, claim 12, for that portion of the formulareading :H: read :1s-+I: and that the said Letters Patent should be readwith th e same may conform to the record of the case in the Pa Signedand sealed this 10th day It is hereb numbered 5, for

ese corrections therein that tent OHce.

of September, A. D. 1946.

LESLIE FRAZER,

First Assistant Commissioner of Patents.

